Apparatus and method for controlling provision of power to a load by a plurality of generating devices

ABSTRACT

An apparatus for controlling provision of power to a load by a plurality of generating devices in a plurality of phased signals during a first operating condition includes: (a) a sensing unit coupled with the load for presenting an indicator relating to load current; and (b) a control unit coupled with the sensing unit for receiving the indicator and coupled with the plurality of generating devices. The control unit presents a first control signal in response to the indicator indicating a second operating condition. The control unit presents a second control signal in response to the indicator indicating a third operating condition. The generating devices respond to the first control signal to substantially simultaneously provide the power to the load. The generating devices respond to the second control signal to substantially provide no power to the load.

This application claims benefit of prior filed copending Provisional Patent Application Ser. No. 60/687,671, filed Jun. 6, 2005.

BACKGROUND OF THE INVENTION

The present invention is directed to electrical power supply devices, and especially to electrical power supply devices generating power using a plurality of generating units operating in a plurality of phases.

One design parameter involved in designing a power supply apparatus is the amount of capacitance one desires or needs at the output of converters providing current to the load. Capacitance may occupy significant area in implementing circuitry, such as power supply circuitry. The amount of capacitance required is at least partially dependent upon the amount of ripple current presented by the power supply device to the load. One benefit of reducing output capacitance is that the power supply apparatus may be configured using less board space and consequently be a smaller portion of a product in which it is employed. In today's marketplace with its emphasis on smaller more compact products, such a reduction in size is beneficial.

Multiphase power supply apparatuses, especially multiphase power supply apparatuses embodied in multiphase converter apparatuses, have evolved to deliver more current to a load that is achievable using a single phase converter apparatus. Multiphase apparatuses contribute other attributes as well such as, by way of example and not by way of limitation, increasing frequency of output ripple current from the power supply apparatus. Such reducing of output ripple current may permit some reduction in size of output capacitance for the power supply apparatus.

However, at least some capacitance is usually necessary for a power supply apparatus because ripple currents produced by inductors in the apparatus generally remain and must be accommodated. Capacitance at the output of a power supply apparatus also permits holding output voltages in regulation between the time a step increase in the load occurs and the time the control loop of the power supply apparatus can respond to the step load increase.

There is a need for an apparatus and method for controlling provision of power to a load by a plurality of generating devices such as a multiphase power supply apparatus that can efficiently respond to a step increase in a load yet minimize capacitance required at the power supply output.

SUMMARY OF THE INVENTION

An apparatus for controlling provision of power to a load by a plurality of generating devices in a plurality of phased signals during a first operating condition includes: (a) a sensing unit coupled with the load for presenting an indicator relating to load current; and (b) a control unit coupled with the sensing unit for receiving the indicator and coupled with the plurality of generating devices. The control unit presents a first control signal in response to the indicator indicating a second operating condition. The control unit presents a second control signal in response to the indicator indicating a third operating condition. The generating devices respond to the first control signal to substantially simultaneously provide the power to the load. The generating devices respond to the second control signal to substantially provide no power to the load.

A method for controlling provision of power to a load by a plurality of generating devices coupled with the load to cooperatively effect providing power to the load in a plurality of phased signals during a first operating condition includes the steps of: (a) In no particular order: (1) providing a sensing unit coupled with the load; and (2) providing a control unit coupled with the sensing unit and coupled with a plurality of selected generating devices of the plurality of generating devices. (b) Operating the sensing unit to present a current indicator relating to sensed current through the load. (c) Operating the control unit to receive the current indicator. (d) When the current indicator indicates a second operating condition, operating the control unit to present at least one first control signal. (e) When the current indicator indicates a third operating condition, operating the control unit to present at least one second control signal. (f) Operating first responsive generating devices of the selected generating devices to substantially simultaneously provide the power to the load in response to the first control signal. (g) Operating second responsive generating devices of the selected generating devices to substantially provide no power to the load in response to the second control signal.

It is, therefore, a feature of the present invention to provide an apparatus and method for controlling provision of power to a load by a plurality of generating devices such as a multiphase power supply apparatus that can efficiently respond to a step increase in a load yet minimize capacitance required at the power supply output.

Further features of the present invention will be apparent from the following specification and claims when considered in connection with the accompanying drawings, in which like elements are labeled using like reference numerals in the various figures, illustrating the preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graphic representation of output current in a power supply device upon application of a step increase of input current.

FIG. 2 is a graphic representation of selected parameters in a power supply device during operation of the present invention.

FIG. 3 is a schematic diagram of an embodiment of the apparatus of the present invention.

FIG. 4 is a schematic diagram of details of the duty cycle control section of the embodiment of the present invention illustrated in FIG. 3.

FIG. 5 is a flow chart illustrating the method of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Multi-phase power supply apparatuses operate pursuant to control by a controller device executing a control loop operation or algorithm. Prior art controller devices operated to balance current through inductors to present power supply output currents in a plurality of phases. The controller device also seeks to maintain balance among phases during transients, such as when a step increase occurs in the load. Prior art controller devices maintain a duty cycle of switches that effect coupling of respective converter devices with the load so that one converter device is providing current to the load at a time. On-time for each respective converter device is fixed to occur at a given time. Off-time for converters is extended to decrease current from the supply to the load. Off-time is decreases to increase current from the supply to the load. Using a prior art control technique sometimes referred to as current mode control (CMC) output voltage is monitored and compared against a reference voltage to ascertain an error voltage. The error voltage typically represents the difference between the output voltage and the reference voltage. The error voltage is used to derive a duty cycle for supply currents that is appropriate to keep the current per phase balanced among phases.

As mentioned earlier herein, capacitance is employed at the output of power supply apparatuses to hold output voltages in regulation during such transient conditions such as step changes in a load. A problem with prior art power supply apparatuses described above is that the control loop employed does not accommodate step changes in load with a sufficiently quick response time. Providing a quick response to load changes, such as step changes in load, can reduce a need for capacitance to hold output voltages in regulation during such transient conditions.

The term “locus” is intended herein to indicate a place, location, locality, locale, point, position, site, spot, volume, juncture, junction or other identifiable location-related zone in one or more dimensions. A locus in a physical apparatus may include, by way of example and not by way of limitation, a corner, intersection, curve, line, area, plane, volume or a portion of any of those features. A locus in an electrical apparatus may include, by way of example and not by way of limitation, a terminal, wire, circuit, circuit trace, circuit board, wiring board, pin, connector, component, collection of components, sub-component or other identifiable location-related area in one or more dimensions. A locus in a flow chart may include, by way of example and not by way of limitation, a juncture, step, site, function, query, response or other aspect, step, increment or an interstice between junctures, steps, sites, functions, queries, responses or other aspects of the flow or method represented by the chart.

FIG. 1 is a graphic representation of output current in a power supply device upon application of a step increase of input current. In FIG. 1, a graphic representation 10 is presented with respect to a horizontal axis 12 indicating time and with respect to a vertical axis 14 indicating current (I). Graphic representation 10 illustrates variation in output current from a supply apparatus. A first curve 20 illustrates a step increase in load current I_(L). Load current I_(L) (curve 20) is substantially steady at a first current level I₁ during a time interval t₀-t₁. At time t₁ load current I_(L) increases in a stepped manner from first current level I₁ to a second current level I₂. The stepped nature of the change in load current I_(L) is manifested in an infinite slope $\left( {{\frac{\mathbb{d}I}{\mathbb{d}t}I_{L}} = \infty} \right)$ at time t₁. After time t₁, load current I_(L) remains substantially steady at second current level I₂.

Output current I_(OUT1) from a power supply unit (not shown in FIG. 1) providing power to the load through which passes load current I_(L) (represented by curve 20) is represented by a second curve 22. Output current I_(OUT1) (curve 22) is substantially steady at first current level I₁ during a time interval t₀-t₁. At time t₁ output current I_(OUT1) responds to the increase in load current I_(L) by increasing after time t₁. Output current I_(OUT1) cannot instantaneously respond to the step change in load current I_(L), so the slope $\left( {\frac{\mathbb{d}I}{\mathbb{d}t}I_{{OUT}\quad 1}} \right)$ of output current I_(OUT1) following time t₁ is less than the substantially infinite slope manifested by load current ${I_{L}\left( {{\frac{\mathbb{d}I}{\mathbb{d}t}I_{{OUT}\quad 1}} < {\frac{\mathbb{d}I}{\mathbb{d}t}I_{L}}} \right)}.$ Output current I_(OUT1) (curve 22) increases from first current level I₁ to second current level I₂ during a time interval t₁-t₃. However, output current I_(OUT1)overshoots second current level I₂ at time t₃ and begins a settling at second current level I₂ that is not complete until a time t₄.

It would be an improvement in response of a power supply apparatus if the step load increase manifested by load current I_(L) could be more closely matched by an output current than is represented by output current I_(OUT1) (curve 22). An example of such a more responsive output current I_(OUT2) is represented by a curve 24. Output current I_(OUT2) responds to the step increase by I_(L) at time t₁ to achieve second current level I₂ at a time t₂. Time t₂ occurs earlier than time t₃ (t₂<t₃). Output current I_(OUT2) is preferably a digitally controlled response to the step change in load current I_(L) so that no significant overshoot occurs and output current I_(OUT2) substantially achieves second current level I₂ at time t₂. The slope $\left( {\frac{\mathbb{d}I}{\mathbb{d}t}I_{{OUT}\quad 2}} \right)$ of output current I_(OUT2) is significantly higher than slope of output current I_(OUT1), yet is not as high as slope of load current I_(L) $\left( {{\frac{\mathbb{d}I}{\mathbb{d}t}I_{{OUT}\quad 3}} < {\frac{\mathbb{d}I}{\mathbb{d}t}I_{{OUT}\quad 2}} < {\frac{\mathbb{d}I}{\mathbb{d}t}I_{L}}} \right).$ That is, output current I_(OUT2) achieves second current level I₂ more rapidly than output current I_(OUT1), but not as rapidly as second current level I₂ is achieved by load current I_(L).

FIG. 2 is a graphic representation of selected parameters in a power supply device during operation of the present invention. Employing the technique illustrated in FIG. 2 permits operating a power supply apparatus to more closely approximate output current I_(OUT2) than I_(OUT1) (FIG. 1) in response to a step change in load current I_(L). In FIG. 2, a graphic representation 40 is presented with respect to a horizontal axis 42 indicating time and with respect to a vertical axis 44 indicating current (I). Graphic representation 40 illustrates the relationship among a source current I_(SOURCE) (represented by a curve 50) being provided to a load (not shown in FIG. 2) by a three phase power supply apparatus using three supply currents φ₁ (represented by a curve 52), φ₂ (represented by a curve 54), φ₃ (represented by a curve 56). Each of supply currents φ₁, φ₂, φ₃ varies between a low level and a high level. Thus supply current φ₁ varies between a low level L₁ and a high level H₁. Supply current φ₂ varies between a low level L₂ and a high level H₂. Supply current φ₃ varies between a low level L₃ and a high level H₃. A load current I_(LOAD) is represented by a curve 58.

Supply current φ₁ is at low level L₁ during time interval t₀-t₁. Supply current φ₁ is at high level H₁ during time interval t₁-t₂. Supply current φ₁ is again at low level L₁ during time interval t₂-t₇. Supply current φ₂ is at low level L₂ during time interval t₀-t₃. Supply current 42 is at high level H₂ during time interval t₃-t₄. Supply current 42 is again at low level L₂ during time interval t₄-t₉. Supply current 43 is at low level L₃ during time interval t₀-t₅. Supply current 43 is at high level H₃ during time interval t₅-t₆. Supply current φ₃ is again at low level L₃ during time interval t₆-t₁₁.

Inspecting FIG. 2, one may observe that first supply current φ₁ has a period T₁ spanning a time interval t₂-t₇; second supply current φ₂ has a period T₂ spanning a time interval t₃-t₉; third supply current φ₃ has a period T₃ spanning a time interval t₅-t₁₁. A first inter-phase interval t₂-t₃ separates first supply current φ₁ and second supply current φ₂. A second inter-phase interval t₄-t₅ separates second supply current 42 and second supply current φ₃. One may observe in FIG. 2 that a first cycle of supply currents φ₁, φ₂, φ₃ spans a time interval t₁-t₆. A second cycle of supply currents φ₁, φ₂, φ₃ begins at time t₇, so there is an inter-cycle interval between a first two successive cycles of supply currents φ₁, φ₂, φ₃ that spans a time interval t₆-t₇.

Load current I_(L) is at a first level I_(L1) during a time interval t₀-t₁₂. At time t₁₂, load current I_(L) increases to a second level I_(L2) in a step-wise fashion, generally as described in connection with curve 20 (FIG. 1) with a substantially infinite slope $\left( \frac{\mathbb{d}I_{L}}{\mathbb{d}t} \right).$ Load current I_(L) remains at second level I_(L2) until time t₁₉. At time t₁₉ load current I_(L) returns to first level I_(L1) in a step-wise fashion with a substantially infinite negative slope $\left( {- \frac{\mathbb{d}I_{L}}{\mathbb{d}t}} \right).$ Load current I_(L) remains at first level I_(L1) after time t₁₉.

During steady-state operations, such as during time interval t₀-t₁₂ (FIG. 2), supply currents φ₁, φ₂, φ₃ cooperate to provide an output or source current I_(SOURCE) at a current level I_(SL1) adequate to meet load current I_(L1). After the step-wise increase of load current I_(L) to a second load current level I_(L2) at time t₁₂, the power supply apparatus (not shown in FIG. 2) tries to keep up with second load current level I_(L2) but cannot keep up completely. In order to avoid a relatively slow reaction, generally as described in connection with curve 22 (FIG. 1) and in order to more closely approach the faster reaction generally described in connection with curve 24 (FIG. 1), all of supply currents φ₁, φ₂, φ₃ are raised to higher levels H₁, H₂, H₃ until source current I_(SOURCE) substantially reaches a level I_(SL2) sufficient to support second load current level I_(L2).

When source current I_(SOURCE) substantially equals second current level I_(SL2) as at time t₁₃, supply currents φ₁, φ₂, φ₃ generally resume their original pattern of operation as described above in connection with time interval t₁-t₇.

At time t₁₉ load current I_(L) returns to first load current level I_(L1) in a step-wise fashion and remains at first load current level I_(L), after time t₁₉. In order to closely follow load current I_(L), all supply currents φ₁, φ₂, φ₃ are set at low levels L₁, L₂, L₃ until source current I_(SOURCE) substantially reaches level I_(SL1) sufficient to support first load current level I_(L1).

Employing multiple supply current phased signals substantially simultaneously to make the power supply more responsive to rapid or step-wise changes in load current reduces variations in output current from the power supply (e.g., I_(SOURCE); FIG. 2), thereby reducing the need for capacitance at the output of the power supply apparatus. Less than all supply current phased signals may be employed simultaneously to effect the desired power supply response to changes in load current. It is preferred that all supply current phased signals be employed simultaneously to effect the desired power supply response to changes in load current.

FIG. 3 is a schematic diagram of an embodiment of the apparatus of the present invention. In FIG. 3, a power supply apparatus 70 having an output locus 80 coupled with a load 72. Load 72 is represented in FIG. 3 as carrying a load current I_(L) and including a switch 74 which controls application of a step current I_(STEP) to load 72. Power supply apparatus 70 includes a plurality of current sources 76 ₁ (providing a first supply current phase φ₁), 76 ₂ (providing a second supply current phase φ₂), 76 ₃ (providing a third supply current phase φ₃), 76 _(n) (providing a nth supply current phase φ_(n)). The indicator “n” is employed to signify that there can be any number of phased current sources in power supply apparatus 70. The inclusion of four phased current sources φ₁, φ₂, φ₃, φ_(n) in FIG. 3 is illustrative only and does not constitute any limitation regarding the number of phased current sources that may be included in the power supply apparatus of the present invention.

Phased current sources φ₁, φ₂, φ₃, φ_(n) are selectively activated in a phased manner substantially as described in connection with supply currents φ₁, φ₂, φ₃ (FIG. 2). Each respective phased current source φ₁, φ₂, φ₃, φ_(n) is selectively coupled with output locus 80 via a respective switch 78 ₁, 78 ₂, 78 ₃, 78 _(n). Each respective switch 78 ₁, 78 ₂, 78 ₃, 78 _(n) responds to actuation signals from an output locus 83 of duty cycle control unit 82, as indicated by an arrow 84. Actuation signal may be provided individually to each respective switch 78 ₁, 78 ₂, 78 ₃, 78 _(n), or a single signal may be employed as an control signal with embedded, coded or otherwise included coding or identification for distinguishing which switch or switches are to be closed or opened to control output current I_(SOURCE) provided by power supply apparatus 70 at output locus 80 for load 72.

A capacitor 86 is coupled in parallel with load 72. A current feedback line 90 is coupled to indicate current I_(C) through capacitor 86. Current I_(C) through capacitor 86 is an indication of total load current I_(LOAD) through load 72. Total load current I_(LOAD) through load 72 includes a load current I_(L) and any step current I_(STEP) that may pass when switch 74 is closed. Current feedback lines 92 ₁, 92 ₂, 92 ₃, 92 _(n) are coupled to respectively indicate currents through phased current sources φ₁, φ₂, φ₃, φ_(n). Current feedback lines 92 _(n) are coupled to a common phased current feedback line 94. Common phased current feedback line 94 thus carries a phased current indication signal I_(φ) indicating phased currents provided to output locus 80. Current feedback line 90 and common phased current feedback line 94 are coupled with a summing node 96 in a manner to effect subtraction of ripple current I_(RIPPLE) present in total load current I_(LOAD) to present a feedback current I_(FB) at a feedback line 98. Feedback line 98 is coupled to provide feedback current I_(FB) to duty cycle control unit 82 and to a summing node 100.

A feedback line 102 provides a feedback voltage V_(FB) from load 72 to a summing node 104. A reference voltage V_(REF) is also provided to summing node 104 in a manner to present an error voltage V_(ERROR) at a feedback line 106. Error voltage V_(ERROR) represents a difference between feedback voltage V_(FB) and reference voltage V_(REF). Feedback line 106 is coupled with summing node 100 in a manner to present a difference indicating signal Δ at a first input 107 to a comparator unit 108. A second input 109 to comparator unit is coupled with common phased current feedback line 94 so that phased current indication signal I_(φ) is presented at second input 109. Comparator unit 108 presents a comparator output signal V_(COMP) at an output locus 110 indicating when difference indicating signal Δ exceeds phased current indication signal I_(φ). Comparator output signal V_(COMP) is provided to duty cycle control unit 82 for use in generating control signals at line 84. Feedback current I_(FB) is also provided to duty cycle control unit 82 via a line 97 for use in generating control signals at line 84.

Provision of an error voltage V_(ERROR) representing difference between feedback voltage V_(FB) and reference voltage V_(REF) (lines 102, 102; summing node 104) for use in comparing with a phased current indication signal I_(φ) indicating phased current sources φ₁, φ₂, φ₃, φ_(n) (comparator unit 108; common phased current feedback line 94; comparator output signal V_(COMP)) employs known techniques sometimes referred to by those skilled in the art as current mode control (CMC).

Using CMC techniques alone, duty cycle control unit 82 may use comparator output signal V_(COMP) to maintain a duty cycle of switches 78 _(n) that effect coupling of respective current sources 76 _(n) with load 72 so that one current source 76 _(n) is providing current to load 72 at a time. On-time for each respective current source 76 _(n) is fixed to occur at a given time. Off-time for current sources 76 _(n) is extended to decrease current to load 72. Off-time is decreased to increase current to load 72. By way of example and not by way of limitation, current sources 76 _(n) may be embodied in a converter device, such as a buck converter, boost converter, a flyback converter or a converter employing another technology or technique.

Using the configuration illustrated in FIG. 3, power supply apparatus 70 may monitor output current (phased current indication signal I_(φ)) and monitor load current (represented by feedback current I_(FB)) to determine when load 72 has significantly changed. When load 72 increases (e.g., at time t₁₂; FIG. 2) duty cycle control unit 82 employs CMC control feedback techniques to monitor output current (phased current indication signal I₁₀₀; comparator output signal V_(COMP)) and uses an indication of load current (feedback current I_(FB)) to identify that power supply apparatus 70 is not fully supplying load 72. In the apparatus of the present invention (FIG. 3), when output current I_(SOURCE) is less than load current I_(LOAD), duty cycle control unit 82 operates to turn on all phased current sources φ₁, φ₂, φ₃, φ_(n) until the cumulative current provided at output locus 80 substantially matches load current I_(LOAD) (represented by feedback current I_(FB)). In the apparatus of the present invention (FIG. 3), when output current I_(SOURCE) is greater than load current I_(LOAD), duty cycle control unit 82 operates to turn off all phased current sources φ₁, φ₂, φ₃, φ_(n) until the cumulative current provided at output locus 80 substantially matches load current I_(LOAD) (represented by feedback current I_(FB)). The technique employed by power supply apparatus 70 effects more efficient current delivery to load 72, thereby reducing const and permitting reduction of output capacitance. Less capacitance is required because ripple current is reduced (summing node 96). The turning on or off of all phased current sources effects transition of output current I_(SOURCE) more quickly so that less time elapses between the time a step increase in load 72 occurs and the time duty cycle control unit 82 can respond to the step load increase. As a consequence there is less time during which output voltages from power supply 70 must be held in regulation, so capacitance is required.

By way of example and not by way of limitation, one may effect turning on fewer than all of phased current sources φ₁, φ₂, φ₃, φ_(n) during ramping up, during ramping down or during both ramping up and ramping down. Different numbers of phased current sources φ₁, φ₂, φ₃, φ_(n) may be turned on for ramping up than may be turned on for ramping down, if desired.

Other parameters may be employed to determine when phased current sources φ₁, φ₂, φ₃, φ_(n) should be turned on or off such as, by way of example and not by way of limitation, rate of rise or fall of load current I_(LOAD), relative rates of rise or fall of load current I_(LOAD) and output current I_(SOURCE), absolute value of difference between load current I_(LOAD) and output current I_(SOURCE), duration of rise or fall of load current I_(LOAD), or other parameters indicating a difference between load current I_(LOAD) and output current I_(SOURCE).

Power supply apparatus 70 avoids a relatively slow reaction, generally as described in connection with curve 22 (FIG. 1) and approximates the faster reaction generally described in connection with curve 24 (FIG. 1).

FIG. 4 is a schematic diagram of details of the duty cycle control section of the embodiment of the present invention illustrated in FIG. 3. In FIG. 4, a duty cycle control unit 82 includes a control signal generator 120, a level setting unit 122 and a control logic unit 124. Control signal generator 120 receives a signal V_(COMP) from a comparator (not shown in FIG. 4; see FIG. 3) and generates control signals Cntrl-φ₁, Cntrl-φ₂, Cntrl-φ₃, Cntrl-φ_(n). Control signals Cntrl-φ₁, Cntrl-φ₂, Cntrl-φ₃, Cntrl-φ_(n) control operation of switches 78 ₁, 78 ₂, 78 ₃, 78 _(n) for connection generation of phased current sources φ₁, φ₂, φ₃, φ_(n) generally as described in connection with FIG. 3. Control signal generator 120 effects production of phased current sources φ₁, φ₂, φ₃, φ_(n) in a timing arrangement generally as described in connection with supply currents φ₁, φ₂, φ₃ during time interval t₁-t₇ (FIG. 2).

Level setting unit 122 includes a first comparator 130 and a second comparator 132. First comparator 130 has a non-inverting input locus 140, an inverting input locus 142 and an output locus 144. An upper reference signal V_(UPPER) is provided at non-inverting input locus 140. Line 97 (FIG. 3) is coupled with inverting input locus 142 so that feedback current I_(FB) is received at inverting input locus 142. When upper reference signal V_(UPPER) is greater than feedback current I_(FB), a “1” is presented at output locus 144. When upper reference signal V_(UPPER) is less than feedback current I_(FB), a “0” is presented at output locus 144.

Second comparator 132 has a non-inverting input locus 150, an inverting input locus 152 and an output locus 154. A lower reference signal V_(LOWER) is provided at inverting input locus 152. Line 97 (FIG. 3) is coupled with non-inverting input locus 150 so that feedback current I_(FB) is received at non-inverting input locus 150. When feedback current I_(FB) is greater than lower reference signal V_(LOWER), a “1” is presented at output locus 154. When feedback current I_(FB) is less than lower reference signal V_(LOWER), a “0” is presented is presented at output locus 154.

Control logic unit 124 includes OR gates 160 ₁, 160 ₂, 160 ₃, 160 _(n); AND gates 164 ₁, 164 ₂, 164 ₃, 164 _(n); and amplifier units 168 ₁, 168 ₂, 168 ₃, 168 _(n). OR gate 160 ₁ receives control signal Cntrl-φ₁ from control signal generator 120 at a first input locus 161 ₁. A second input locus 162 ₁ is coupled with output locus 144 of first comparator 130. OR gate 160 ₁ presents a logical OR output signal at an output locus 163 ₁ that is established by values of signals applied at input loci 161 ₁, 162 ₁. AND gate 164 ₁ receives the logical OR output signal from output locus 163 ₁ at a first input locus 165 ₁. A second input locus 166 ₁ is coupled with output locus 154 of first comparator 132. AND gate 164 ₁ is configured to invert signals received at second input locus 166 ₁. AND gate 164 ₁ presents a logical AND output signal at an output locus 167 ₁ that is established by value of the signal applied at input locus 165 ₁ and the inverse of the signal applied at input locus 166 ₁. Amplifier 168 ₁ receives the output signal presented at output locus 167 ₁ and presents a control signal Cntrl₁-φ₁ at an output locus 83 ₁. Control signal Cntrl₁-φ₁ is applied to control switch 78 ₁ (FIG. 3). As described earlier herein, actuation signals presented as indicated by arrow 84 (FIG. 3) may be provided individually to each respective switch 78 ₁, 78 ₂, 78 ₃, 78 _(n), or a single signal may be employed as an control signal with embedded, coded or otherwise included coding or identification for distinguishing which switch or switches are to be closed or opened to control output current I_(SOURCE) provided by power supply apparatus 70 at output locus 80 for load 72. FIG. 4 illustrates an example in which actuation signal Cntrl₁-φ₁ is provided individually to switch 781.

OR gate 160 ₂ receives control signal Cntrl-φ₂ from control signal generator 120 at a first input locus 161 ₂. A second input locus 162 ₂ is coupled with output locus 144 of first comparator 130. OR gate 160 ₂ presents a logical OR output signal at an output locus 163 ₂ that is established by values of signals applied at input loci 161 ₂, 162 ₂. AND gate 164 ₂ receives the logical OR output signal from output locus 163 ₂ at a first input locus 165 ₂. A second input locus 166 ₂ is coupled with output locus 154 of first comparator 132. AND gate 164 ₂ is configured to invert signals received at second input locus 166 ₂. AND gate 164 ₂ presents a logical AND output signal at an output locus 167 ₂ that is established by value of the signal applied at input locus 165 ₂ and the inverse of the signal applied at input locus 166 ₁. Amplifier 168 ₁ receives the output signal presented at output locus 167 ₂ and presents a control signal Cntrl₁-φ₂ at an output locus 83 ₂. Control signal Cntrl₁-φ₂ is applied to control switch 78 ₂ (FIG. 3). As described earlier herein, actuation signals presented as indicated by arrow 84 (FIG. 3) may be provided individually to each respective switch 78 ₁, 78 ₂, 78 ₃, 78 _(n), or a single signal may be employed as an control signal with embedded, coded or otherwise included coding or identification for distinguishing which switch or switches are to be closed or opened to control output current I_(SOURCE) provided by power supply apparatus 70 at output locus 80 for load 72. FIG. 4 illustrates an example in which actuation signal Cntrl₁-φ₂ is provided individually to switch 78 ₂.

OR gate 160 ₃ receives control signal Cntrl-φ₃ from control signal generator 120 at a first input locus 161 ₃. A second input locus 162 ₃ is coupled with output locus 144 of first comparator 130. OR gate 160 ₃ presents a logical OR output signal at an output locus 163 ₃ that is established by values of signals applied at input loci 161 ₃, 162 ₃. AND gate 164 ₃ receives the logical OR output signal from output locus 163 ₃ at a first input locus 165 ₃. A second input locus 166 ₃ is coupled with output locus 154 of first comparator 132. AND gate 164 ₃ is configured to invert signals received at second input locus 166 ₃. AND gate 164 ₃ presents a logical AND output signal at an output locus 167 ₃ that is established by value of the signal applied at input locus 165 ₃ and the inverse of the signal applied at input locus 166 ₃. Amplifier 168 ₃ receives the output signal presented at output locus 167 ₃ and presents a control signal Cntrl₁-φ₃ at an output locus 83 ₃. Control signal Cntrl₁-φ₃ is applied to control switch 78 ₃ (FIG. 3). As described earlier herein, actuation signals presented as indicated by arrow 84 (FIG. 3) may be provided individually to each respective switch 78 ₁, 78 ₂, 78 ₃, 78 _(n), or a single signal may be employed as an control signal with embedded, coded or otherwise included coding or identification for distinguishing which switch or switches are to be closed or opened to control output current I_(SOURCE) provided by power supply apparatus 70 at output locus 80 for load 72. FIG. 4 illustrates an example in which actuation signal Cntrl₁-φ₃ is provided individually to switch 78 ₃.

OR gate 160 _(n) receives control signal Cntrl-φ_(n) from control signal generator 120 at a first input locus 161 _(n). A second input locus 162 _(n) is coupled with output locus 144 of first comparator 130. OR gate 160 _(n) presents a logical OR output signal at an output locus 163 _(n) that is established by values of signals applied at input loci 161 _(n), 162 _(n). AND gate 164 _(n) receives the logical OR output signal from output locus 163 _(n) at a first input locus 165 _(n). A second input locus 166 _(n) is coupled with output locus 154 of first comparator 132. AND gate 164 _(n), is configured to invert signals received at second input locus 166 _(n). AND gate 164 _(n) presents a logical AND output signal at an output locus 167 _(n) that is established by value of the signal applied at input locus 165 _(n) and the inverse of the signal applied at input locus 166 _(n). Amplifier 168 _(n) receives the output signal presented at output locus 167 _(n) and presents a control signal Cntrl₁-φ_(n) at an output locus 83 _(n). Control signal Cntrl₁-φ_(n) is applied to control switch 78, (FIG. 3). As described earlier herein, actuation signals presented as indicated by arrow 84 (FIG. 3) may be provided individually to each respective switch 78 ₁, 78 ₂, 78 ₃, 78 _(n), or a single signal may be employed as an control signal with embedded, coded or otherwise included coding or identification for distinguishing which switch or switches are to be closed or opened to control output current I_(SOURCE) provided by power supply apparatus 70 at output locus 80 for load 72. FIG. 4 illustrates an example in which actuation signal Cntrl₁-φ_(n) is provided individually to switch 78 _(n).

Inspecting FIG. 4, one may observe that so long as feedback current I_(FB) is greater than V_(LOWER) and less than V_(UPPER) control signals Cntrl-φ₁, Cntrl-φ₂, Cntrl-φ₃, Cntrl-φ_(n) will be substantially unimpeded by control logic unit 124 to contribute substantially directly in amplitude and phase to actuation signals Cntrl₁-φ₁, Cntrl₁-φ₂, Cntrl₁-φ₃, Cntrl₁-φ_(n) at output loci 83 _(n).

When feedback current I_(FB) is less than V_(LOWER) a “1” signal is presented at input loci 166 _(n) and inverted to appear as a “0” signal to AND gates 164 _(n). As a consequence, whatever control signal Cntrl-φ_(n) is provided at inputs 161 _(n) of OR gates 160 _(n), a “0” signal is presented at output loci 167 _(n). This indicates that less current is required from power supply apparatus 70. This circumstance is present, by way of example and not by way of limitation, during time interval t₁₉-t₂₀ (FIG. 2).

When feedback current I_(FB) is greater than V_(UPPER) a “0” signal is presented at input loci 166 _(n) and inverted to appear as a “1” signal to AND gates 164 _(n), and a “1” signal is presented at input loci 162 _(n) to OR gates 160 _(n) assuring that the logical OR output of OR gates 160 _(n) will be a “1” signal. AND gates 164 _(n) will therefore present a “1” signal at output loci 167 _(n) so that whatever control signal Cntrl-φ_(n) is provided at inputs 161 _(n) of OR gates 160 _(n), a “1” signal is presented at output loci 163 _(n). This indicates that more current is required from power supply apparatus 70. This circumstance is present, by way of example and not by way of limitation, during time interval t₁₂-t₁₃ (FIG. 2).

FIG. 5 is a flow chart illustrating the method of the present invention. In FIG. 5, a method 200 for controlling provision of power to a load by a plurality of generating devices begins at a START locus 202. The plurality of generating devices are coupled with the load to cooperatively effect providing the power to the load in a plurality of substantially non-simultaneous phased signals during a first operating condition. Method 200 continues with, in no particular order: (1) providing a sensing unit coupled with the load, as indicated by a block 204; and (2) providing a control unit coupled with the sensing unit and coupled with a plurality of selected generating devices of the plurality of generating devices, as indicated by a block 205.

Method 200 continues with operating the sensing unit to present a current indicator relating to sensed current through the load, as indicated by a block 206. Method 200 continues with operating the control unit to receive the current indicator, as indicated by a block 208.

Method 200 continues by posing a query whether the current indicator indicates a second operating condition, as indicated by a block 210. If the current indicator indicates a second operating condition, method 200 proceeds via YES response line 212 to effect operating the control unit to present at least one first control signal, as indicated by a block 216. Method 200 continues with operating the generating devices to provide power, as indicated by a block 218.

Method 200 continues by posing a query whether the operating condition has changed, as indicated by a block 220. If the operating condition has not changed, method 200 proceeds via NO response line 224 and continues operating the generating devices to provide power, as indicated by block 218. If the operating condition has changed, method 200 proceeds via YES response line 222 and returns to locus 226 to continue.

If at the time of posing the query indicated by query block 210 the current indicator does not indicate a second operating condition, method 200 proceeds from query block 210 via NO response line 214 and another query is posed whether the current indicator indicates a third operating condition, as indicated by a block 230. If the current indicator indicates a third operating condition, method 200 proceeds via YES response line 232 to effect operating the control unit to present at least one second control signal, as indicated by a block 236. Method 200 continues with operating the generating devices to provide no power, as indicated by a block 238.

Method 200 continues by posing a query whether the operating condition has changed, as indicated by a block 240. If the operating condition has not changed, method 200 proceeds via NO response line 244 and continues operating the generating devices to provide no power, as indicated by block 238. If the operating condition has changed, method 200 proceeds via YES response line 242 and returns to locus 226 to continue.

If at the time of posing the query indicated by query block 230 the current indicator does not indicate a third operating condition, method 200 proceeds from query block 230 via NO response line 234 and returns to locus 226 to continue.

As mentioned hereinbefore, one of the parameters in selecting the output capacitance bank for a converter such as may be embodied in phased current sources φ₁, φ₂, φ₃, φ_(n) (FIG. 3) is the ripple current entering the capacitance bank from the power supply apparatus. The power supply apparatus uses inductors to convert an input voltage received from an input voltage bus to a new voltage on the output side of the converter. Under certain conditions, the ripple current can be reduced and the source can approximate a DC (Direct Current) source.

N-phase power supply apparatuses reduce ripple current because of the net effect of having n converters out of phase increases the output ripple frequency by a factor of n. This increase in ripple current frequency improves output ripple current. However, it is known that certain topologies (like the dual-interleaved forward) produce zero ripple current under specific situations. By way of example and not by way of limitation, a dual-interleaved forward topology operating at 50% duty cycle for each phase produces nearly zero ripple. By way of another example, the turns ratio of an output transformer for a power supply apparatus may be adjusted to present a zero-ripple current at a particular input voltage.

Another approach to making a zero ripple machine where the input voltage is fixed and the output voltage is regulated may be by staggering n-phases at some multiple of the inherent duty cycle (e.g., in the case of non-isolated buck converters). The duty cycle on a buck converter is proportional to the output voltage divided by the input voltage moderated by the voltage losses due to switches, diodes, and transformer leakages. In a non-isolated buck, there can be a particular number of phases that will produce a zero-ripple output. However, the particular number of phases is not driven by the current carrying capability of each phased current source rather than being driven by the zero ripple requirement.

Such solutions to presenting a zero-ripple output have proven satisfactory so long as one happens to need exactly the right number of phases and so long as the input voltage is totally tunable to obtain the desired resultant output. These are design restrictions not often accommodated by applications in which a power supply apparatus may be employed.

In the preferred embodiment of the present invention improved achievement of a zero-ripple output may be realized by replacing a single winding (2 pin) inductor with a more complex multi-tapped inductor (e.g., 3 or 4 pins) in order that the output ripple current can be reduced to near zero, or zero ripple current. Providing a multi-tapped inductor structure permits selecting a tap to establish an approximate desired turns ratio such that the inherent duty cycle produces zero ripple.

A design process for such an improved zero-ripple output apparatus may involve first determining the maximum current to be experienced per phase in the apparatus. The maximum current per phase is controlled by the thermal profile of the design. Given the trend of the marketplace toward ever smaller more compact products, design objectives for the apparatus are presumed to include small size. A small size encourages a higher switching frequency. A higher switching frequency creates more switching losses and leaves less room in the thermal profile for conduction losses. Once the maximum current per phase is determined, the maximum current divided by the current per phase yields the number of phases required.

This design process presumes that the input voltage is relatively constant. Voltage losses across the active elements may determined and the inherent duty cycle may be calculated. ( $\frac{V_{OUT}}{V_{IN}},$ modified by the losses).

The turns ratio to make the duty cycle of the apparatus produce a zero-ripple output may now be determined. There are several solutions that can be implemented here. By way of example and not by way of limitation, five channels could be configured to operate at a 20% duty cycle each. Alternatively, five channels could be configured to operate at a 40% duty cycle each. Both solutions will yield a zero current converter. The 40% duty cycle solution will step from maximum output to minimum output, and will step from minimum output to maximum output quickly. The 20% duty cycle solution will step from minimum output to maximum output quickly, but will step from maximum output to minimum output more slowly. These considerations may be taken into account in selecting number of channels n and duty cycle characteristics to design an apparatus for requirements of a particular application.

The turns ratio must necessarily be a whole number and it is known to be better if the turns ratio is kept small. Keeping the number of turns small is consistent with the design goal of making the apparatus small. However, the integer turn ratio may not align precisely with a desired turns ratio for producing a zero-ripple output. Such a between a desired turns ratio and an actual turns ratio may yield a discontinuity in the zero ripple output. The inventor has observed that overlapping the duty cycle among phased current sources φ₁, φ₂, φ₃, φ_(n) can improve performance when accepting a lesser turns ratio than the desired turns ratio. Additionally, it may be possible in particular application to increase or decrease the input voltage to achieve a zero ripple output. These considerations are substantially equally valid to buck, boost, and flyback topologies.

It is to be understood that, while the detailed drawings and specific examples given describe preferred embodiments of the invention, they are for the purpose of illustration only, that the apparatus and method of the invention are not limited to the precise details and conditions disclosed and that various changes may be made therein without departing from the spirit of the invention which is defined by the following claims: 

1. An apparatus for controlling operation of a power supply device providing power to a load in a plurality of phases; said power supply device including a plurality of generating devices coupled with said load; each respective generating device of said plurality of generating devices providing power to said load in a respective phase of said plurality of phases during a first operating condition; the apparatus comprising: (a) a sensing unit coupled for sensing an indicator relating to current through said load; and (b) a control unit coupled with said sensing unit and with each said respective generating device; said control unit generating at least one first control signal in response to said indicator indicating a second operating condition; first selected said generating devices of said plurality of generating devices substantially simultaneously providing said power to said load in response to said at least one first control signal at least as long as said indicator indicates said second operating condition.
 2. An apparatus for controlling operation of a power supply device providing power to a load in a plurality of phases as recited in claim 1 wherein said second operating condition is extant when said indicator indicates current through said load is greater than a predetermined first current level.
 3. An apparatus for controlling operation of a power supply device providing power to a load in a plurality of phases as recited in claim 1 wherein said first selected generating devices include all of said plurality of generating devices.
 4. An apparatus for controlling operation of a power supply device providing power to a load in a plurality of phases as recited in claim 3 wherein said second operating condition is extant when said indicator indicates current through said load is greater than a predetermined first current level.
 5. An apparatus for controlling operation of a power supply device providing power to a load in a plurality of phases as recited in claim 1 wherein said indicator is said current through said load.
 6. An apparatus for controlling operation of a power supply device providing power to a load in a plurality of phases as recited in claim 5 wherein said second operating condition is extant when said current through said load is greater than a predetermined first current level.
 7. An apparatus for controlling operation of a power supply device providing power to a load in a plurality of phases as recited in claim 5 wherein said first selected generating devices include all of said plurality of generating devices.
 8. An apparatus for controlling operation of a power supply device providing power to a load in a plurality of phases as recited in claim 1 wherein said second operating condition is extant when said indicator indicates current through said load is greater than a predetermined first current level; wherein said control unit generates at least one second control signal in response to said indicator indicating a third operating condition; said third operating condition being extant when said indicator indicates current through said load is less than a predetermined second current level; said second current level being lower than said first current level; and wherein second selected said generating devices of said plurality of generating devices substantially simultaneously provide no power to said load in response to said at least one second control signal at least as long as said indicator indicates said third operating condition.
 9. An apparatus for controlling operation of a power supply device providing power to a load in a plurality of phases as recited in claim 8 wherein said first selected generating devices include all of said plurality of generating devices, and wherein said second selected generating devices include all of said plurality of generating devices.
 10. An apparatus for controlling operation of a power supply device providing power to a load in a plurality of phases as recited in claim 9 wherein said indicator is said current through said load.
 11. An apparatus for controlling provision of power to a load by a plurality of generating devices; said plurality of generating devices being coupled with said load to cooperatively effect providing said power to said load in a plurality of substantially non-simultaneous phased signals during a first operating condition; the apparatus comprising: (a) a sensing unit coupled with said load for presenting a current indicator relating to sensed current through said load; and (b) a control unit coupled with said sensing unit for receiving said current indicator and coupled with a plurality of selected generating devices of said plurality of generating devices; said control unit presenting at least one first control signal in response to said current indicator indicating a second operating condition; said control unit presenting at least one second control signal in response to said current indicator indicating a third operating condition; first responsive generating devices of said selected generating devices responding to said first control signal to substantially simultaneously provide said power to said load; second responsive generating devices of said selected generating devices responding to said second control signal to substantially provide no power to said load.
 12. An apparatus for controlling provision of power to a load by a plurality of generating devices as recited in claim 11 wherein said plurality of selected generating devices is all of said plurality of generating devices.
 13. An apparatus for controlling provision of power to a load by a plurality of generating devices as recited in claim 11 wherein said first responsive generating devices is all of said plurality of generating devices.
 14. An apparatus for controlling provision of power to a load by a plurality of generating devices as recited in claim 11 wherein said second responsive generating devices is all of said plurality of generating devices.
 15. An apparatus for controlling provision of power to a load by a plurality of generating devices as recited in claim 11 wherein said second operating condition is extant when said current through said load is greater than a predetermined first current level.
 16. An apparatus for controlling provision of power to a load by a plurality of generating devices as recited in claim 11 wherein said third operating condition is extant when said current through said load is less than a predetermined second current level; said second current level being lower than said first current level.
 17. A method for controlling provision of power to a load by a plurality of generating devices; said plurality of generating devices being coupled with said load to cooperatively effect providing said power to said load in a plurality of substantially non-simultaneous phased signals during a first operating condition; the method comprising the steps of: (a) in no particular order: (1) providing a sensing unit coupled with said load; and (2) providing a control unit coupled with said sensing unit and coupled with a plurality of selected generating devices of said plurality of generating devices; (b) operating said sensing unit to present a current indicator relating to sensed current through said load; (c) operating said control unit to receive said current indicator; (d) when said current indicator indicates a second operating condition, operating said control unit to present at least one first control signal; (e) when said current indicator indicates a third operating condition, operating said control unit to present at least one second control signal; (f) operating first responsive generating devices of said selected generating devices to substantially simultaneously provide said power to said load in response to said first control signal; and (g) operating second responsive generating devices of said selected generating devices to substantially provide no power to said load in response to said second control signal.
 18. A method for controlling provision of power to a load by a plurality of generating devices as recited in claim 17 wherein said plurality of selected generating devices is all of said plurality of generating devices.
 19. A method for controlling provision of power to a load by a plurality of generating devices as recited in claim 17 wherein said first responsive generating devices is all of said plurality of generating devices, and wherein said second responsive generating devices is all of said plurality of generating devices.
 20. A method for controlling provision of power to a load by a plurality of generating devices as recited in claim 17 wherein said second operating condition is extant when said current through said load is greater than a predetermined first current level, and wherein said third operating condition is extant when said current through said load is less than a predetermined second current level; said second current level being lower than said first current level. 